Pulsed plasma (DC/RF) deposition of high quality C films for patterning

ABSTRACT

Methods for depositing an amorphous carbon layer onto a substrate, including over previously formed layers on the substrate, use a plasma-enhanced chemical vapor deposition (PECVD) process. In particular, the methods utilize a combination of RF AC power and pulsed DC power to create a plasma which deposits an amorphous carbon layer with a high ratio of sp3 (diamond-like) carbon to sp2 (graphite-like) carbon. The methods also provide for lower processing pressures, lower processing temperatures, and higher processing powers, each of which, alone or in combination, may further increase the relative fraction of sp3 carbon in the deposited amorphous carbon layer. As a result of the higher sp3 carbon fraction, the methods provide amorphous carbon layers having improved density, rigidity, etch selectivity, and film stress as compared to amorphous carbon layers deposited by conventional methods.

BACKGROUND Field

Embodiments of the present disclosure relate to methods for depositingan amorphous carbon layer onto a substrate, including over previouslyformed layers on the substrate, using a plasma-enhanced chemical vapordeposition (PECVD) process.

Description of the Related Art

Carbon hardmasks formed of amorphous carbon are used in semiconductordevice manufacturing as an etching mask in forming high aspect ratioopenings (e.g., a height to width ratio of 2:1 or more) in a substratesurface or in a material surface layer thereof. Generally, processingissues related to forming high aspect ratio openings, includingclogging, hole-shape distortion, pattern deformation, top criticaldimension blow up, line bending, and profile bowing are a result ofundesirable material properties of conventionally deposited carbonhardmasks. For example, carbon hardmasks having one or both of lowermaterial density and lower material rigidity (i.e., Young's modulus) areknown to cause increased deformation of high aspect ratio openings whencompared to hardmask materials having a higher density or higherrigidity.

Likewise, reduced etch selectivity between hardmask materials andsubstrate materials can cause increased slit pattern deformation andline bending as compared to hardmasks exhibiting higher etchselectivity. Similar problems may be caused by high film stress(compressive or tensile). Further, as critical dimensions (CDs) shrinkand the magnitude of high aspect ratio openings increase, the thicknessof conventionally deposited carbon hardmask used to form the high aspectratio openings also increases. Unfortunately, hardmasks having lowertransparency due to one or both of low optical K and increased thicknesscan cause misalignment in subsequent photolithography processes.Further, processes having lower etch selectivity between the hardmaskmaterial and the underlying substrate material often rely uponrelativity thicker hardmasks which increase processing time and cost.

Accordingly, what is needed in the art are improved hardmasks andmethods of forming improved hardmasks.

SUMMARY

In one embodiment, a method of processing a substrate is provided. Themethod includes positioning a substrate on a substrate support disposedin a process volume of a process chamber. The method further includesflowing a process gas comprising a hydrocarbon gas and a diluent gasinto the process volume. The method further includes maintaining theprocess volume at a pressure less than about 100 mTorr. The methodfurther includes forming a plasma of the process gas by applying a firstpower to a first electrode of the process chamber and applying a secondpower to a second electrode of the process chamber, wherein the secondpower is a pulsed DC power. The method further includes maintaining thesubstrate support at a temperature less than about 350° C. The methodfurther includes exposing a surface of the substrate to the plasma. Themethod further includes depositing an amorphous carbon layer on thesurface of the substrate.

In another embodiment, a method of processing a substrate is provided.The method includes positioning a substrate on a substrate supportdisposed in a process volume of a process chamber. The method furtherincludes flowing a process gas comprising a hydrocarbon gas and adiluent gas into the process volume. The method further includesmaintaining the process volume at a pressure less than about 20 mTorr.The method further includes forming a plasma of the process gas byapplying an RF AC power to a first electrode of the process chamber,wherein the RF AC power is between about 500 W and 5 kW, with afrequency between about 350 kHz and about 100 MHz and applying a pulsedDC power to a second electrode of the process chamber, wherein thepulsed DC power is between about 200 W and about 15 kW pulsed at afrequency of about 1 kHz. The method further includes maintaining thesubstrate support at a temperature less than about 100° C. The methodfurther includes exposing a surface of the substrate to the plasma. Themethod further includes depositing an amorphous carbon layer on thesurface of the substrate.

In another embodiment, a carbon hardmask is provided. The carbonhardmask includes an amorphous carbon layer disposed on a surface of asubstrate. The amorphous carbon layer has a density of more than about1.8 g/cm³, a Young's modulus of more than about 150 GPa, and a filmstress of less than about 500 MPa.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 illustrates a schematic cross-sectional view of an exemplaryprocessing chamber used to practice the methods set forth herein,according to one embodiment.

FIG. 2 illustrates a flow diagram of a method of depositing an amorphouscarbon layer, according to one embodiment.

FIG. 3 illustrates a carbon hardmask formed of an amorphous carbon layerdeposited according to the method set forth in FIG. 2 , according to oneembodiment.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate to methods for depositingan amorphous carbon layer onto a substrate, including over previouslyformed layers on the substrate, using a plasma-enhanced chemical vapordeposition (PECVD) process. In particular, the methods described hereinutilize a combination of RF AC power and pulsed DC power to create aplasma which deposits an amorphous carbon layer with a high ratio of sp3(diamond-like) carbon to sp2 (graphite-like) carbon. The methods alsoprovide for lower processing pressures, lower processing temperatures,and higher processing powers, each of which, alone or in combination,may further increase the relative fraction of sp3 carbon in thedeposited amorphous carbon layer. As a result of the higher sp3 carbonfraction, the methods described herein provide amorphous carbon layershaving improved density, rigidity, etch selectivity, and film stress ascompared to amorphous carbon layers deposited by conventional methods.

FIG. 1 is a schematic cross sectional view of an exemplary processingchamber 100 used to practice the methods set forth herein, according toone embodiment. Other exemplary processing chambers that may be used topractice the methods describe herein include RADION™, PRODUCER®, andSYM3™ processing apparatus available from Applied Materials, Inc., ofSanta Clara, Calif. as well as suitable deposition chambers from othermanufacturers.

The processing chamber 100 includes a lid assembly 101, sidewalls 102,and a chamber base 104. The lid assembly 101 includes a chamber lid 106,a showerhead 107 coupled to the chamber lid 106 and in electricalcommunication therewith, and an electrically insulating ring 108disposed between the chamber lid 106 and the sidewalls 102. Theshowerhead 107, the sidewalls 102, and the chamber base 104 togetherdefine a processing volume 105. In one embodiment, the chamber lid 106and the showerhead 107 are formed from an electrically conductivelymaterial such as aluminum. A gas inlet 109 is disposed through thechamber lid 106 and fluidly coupled to a gas source 110. The showerhead107, having a plurality of openings 111 disposed therethrough, is usedto uniformly distribute processing gases from the gas source 110 intothe processing volume 105. In other embodiments, the processing chamber100 does not include a showerhead 107, and processing gases aredelivered to the processing volume 105 through one or more gas inletsdisposed through the chamber lid 106 or the sidewalls 102.

The processing volume 105 is fluidly coupled to a vacuum source 112,which may be one or more dedicated vacuum pumps, through a vacuum outlet114, which maintains the processing volume 105 at sub-atmosphericconditions and evacuates the processing gas and other gases therefromduring processing. A substrate support 115, disposed in the processingvolume 105, is disposed on a movable support shaft 116 extending throughthe chamber base 104. Herein, the processing chamber 100 is configuredto facilitate transferring of a substrate 117 to and from the substratesupport 115 through an opening 118 in one of the one or more sidewalls102, which is sealed with a door or a valve (not shown) during substrateprocessing.

The substrate 117 is maintained at a desired processing temperatureusing one or both of a heater 119 and one or more cooling channels 120.The heater 119, which may be a resistive heater, and the one or morecooling channels are disposed in the substrate support 115. The one ormore cooling channels 120 are fluidly coupled to a coolant source (notshown), such as a refrigerant source or a modified water source havingrelatively high electrical resistance. The heater 119 is in electricalcommunication with a power source (not shown) which is configured topower the heater 119 and elevate a temperature of the substrate support115.

In some embodiments, one or more electrodes 124 are embedded in adielectric material of the substrate support 115. The one or moreelectrodes are electrically coupled to a power supply 121. A powersupply 122 is electrically coupled to the showerhead 107. Forembodiments which do not include a showerhead, the power supply 122 iselectrically coupled to the lid assembly 106. Each of the power supplies121 and 122 may be a continuous wave (CW) RF power supply, a pulsed RFpower supply, a DC power supply, and/or a pulsed DC power supply. In oneembodiment, the power supply 121 is a CW RF power supply, and the powersupply 122 is a pulsed DC power supply. In another embodiment, the powersupply 121 is a pulsed DC power supply, and the power supply 122 is apulsed RF power supply. While only two power supplies 121 and 122 areshown, it is contemplated that more power supplies may be coupled toelectrodes in either the substrate support 115 or the lid assembly 101as needed. For instance, pulsed DC power supplies may be coupled toelectrodes in both the substrate support 115 and the lid assembly 101,along with an RF supply coupled to electrodes in the lid assembly 101.

In one embodiment, a plasma 123 is formed and maintained in theprocessing volume 105 by providing RF power from the power supply 122 toone or more electrodes in the lid assembly 101, thereby creating acapacitively coupled plasma 123. The plasma 123 is then modified byproviding DC power from the power supply 121 to one or more electrodesdisposed in the substrate support 115. In another embodiment, the plasma123 is formed and maintained by RF power from the power supply 121 andmodified by DC power from the power supply 122.

FIG. 2 is a flow diagram of a method 200 of depositing an amorphouscarbon layer on a surface of a substrate, according to one embodiment.At operation 201 the method 200 includes positioning a substrate on asubstrate support. The substrate support is disposed in a processingvolume of a processing chamber, such as the processing chamber 100described in FIG. 1 . At operation 202 the method 200 includes flowing aprocessing gas into the processing volume. The processing gas includes acarbon source gas, such as a hydrocarbon gas, for example CH₄, C₂H₂,C₃H₈, C₄H₁₀, C₂H₄, C₃H₆, C₄H₈, C₅H₁₀, or combinations thereof. and theprocessing gas also includes a diluent gas, for example an inert gassuch as Ar, He, Ne, Kr, Xe, or combinations thereof. In someembodiments, the diluent gas includes inert gases, such as a noblegases, N₂, H₂, or combinations thereof.

In some embodiments, a ratio of the flowrate of the hydrocarbon gas tothe flowrate of the diluent gas is between about 1:10 and about 10:1,such as between about 1:5 and about 5:1. For example, in one embodimenta ratio of a flowrate of C₂H₂ to a flowrate of He is between about 1:3and about 3:1. In some embodiments, the diluent gas includes H₂ and aratio of the flowrate of H₂ to the flowrate of hydrocarbon gas isbetween about 0.5:1 and about 1:10, such as between about 1:1 and about1:5.

At operation 203, the method 200 includes maintaining the processingvolume at a processing pressure between about 0.1 mTorr and about 100mTorr, such as between about 0.1 mTorr and about 50 mTorr, or betweenabout 0.1 mTorr and about 30 mTorr, or between about 0.1 mTorr and about20 mTorr, or between about 0.1 mTorr and about 15 mTorr, or betweenabout 0.1 mTorr and about 10 mTorr, or less than about 100 mTorr, orless than about 50 mTorr, or less than about 20 mTorr, or less thanabout 15 mTorr, or less than about 10 mTorr.

At operation 204, the method 200 includes forming and maintaining aplasma of the processing gas by applying a first power to a firstelectrode of the processing chamber and applying a second power to asecond electrode of the processing chamber, wherein the second power isa pulsed DC power. In one embodiment, the first electrode is disposed inthe substrate support. In another embodiment, the first electrode isdisposed opposite the substrate support, such as in a showerhead orchamber lid of the processing chamber. In one embodiment, the firstpower is an RF AC power between about 500 W and about 5 kW, such asabout 2500 W. The first power has a frequency between about 350 kHz andabout 100 MHz, such as 2 MHz or 13.56 MHz.

In one embodiment, the second electrode is disposed in the substratesupport. In another embodiment, the second electrode is disposedopposite the substrate support. In one embodiment, the second electrodeis a showerhead. In one embodiment, the second power is between about200 W and about 15 kW. In another embodiment, the second power is pulsedat a frequency of about 1 kHz. In another embodiment, the second powerhas a duty cycle of about 50%.

It is believed that providing a pulsed DC power from the substratesupport, as described above, results in greater uniformity of ionenergies within the plasma, which in turn leads to a higherconcentration of sp3 carbon in the deposited amorphous carbon layer. Asdescribed below with respect to FIG. 3 , amorphous carbon layers withhigher sp3 concentrations demonstrate desirable properties such ashigher density, higher Young's modulus, and lower film stress ascompared to conventionally-deposited amorphous carbon layers. It isfurther believed that providing a pulsed DC power opposite the substratesupport, e.g., to a second electrode such as a showerhead, as describedabove, results in increased secondary electron emission from the secondelectrode, which can further reduce the film stress of the depositedamorphous carbon layer.

At operation 205 the method 200 includes maintaining the substratesupport, and thus the substrate disposed thereon, at a temperaturebetween about −50° C. and about 350° C., such as between about −50° C.and about 150° C., between about −50° C. and about 100° C., betweenabout −50° C. and about 50° C., between about −25° C. and about 25° C.,or a temperature less than about 350° C., such as less than about 200°C., less than about 150° C., less than 100° C., or less than about 50°C.

At operation 206, the method 200 includes exposing a surface of thesubstrate to the plasma. At operation 207, the method 200 includesdepositing an amorphous carbon layer on the surface of the substrate.

While FIG. 2 illustrates one example of a flow diagram, it is to benoted that variations of method 200 are contemplated. For example, it iscontemplated that operation 205 may occur prior to operation 202, 203,or 204. Additionally, it is contemplated that one or more of operations202-207 may occur concurrently.

FIG. 3 illustrates a carbon hardmask 303 deposited according to themethod set forth in FIG. 2 , according to one embodiment. The carbonhardmask 303, shown as a patterned carbon hardmask, includes anamorphous carbon layer 302, having a plurality of openings 304 formedtherein, disposed on a to-be-patterned surface of a substrate 301. Thesubstrate 301 or one or more material layers thereof are formed of oneor a combination of crystalline silicon, silicon oxide, siliconoxynitride, silicon nitride, strained silicon, silicon germanium,tungsten, titanium nitride, doped or undoped polysilicon, carbon dopedsilicon oxides, silicon nitrides, doped silicon, germanium, galliumarsenide, glass, sapphire, and low k dielectric materials.

The amorphous carbon layer 302 has a thickness between about 1 kÅ andabout 40 kÅ, such as between about 10 kÅ and about 40 kÅ or betweenabout 10 kÅ and about 30 kÅ, a density of more than about 1.8 g/cm³, anda Young's modulus of more than about 150 GPa. In one embodiment, theamorphous carbon layer 302 has a tensile or compressive film stress ofless than about 500 MPa. In some embodiments, each of the openings 304have an aspect ratio (i.e., a ratio of height 306 to width 305) of morethan about 2:1, such as more than about 3:1, more than about 4:1, morethan about 5:1, more than about 6:1, more than about 7:1, more thanabout 8:1, more than about 9:1, or more than about 10:1.

The methods described herein and the amorphous carbon layers depositedaccording to such methods exhibit desirable properties for carbonhardmask applications. The deposited amorphous carbon layers exhibit ahigh ratio of sp3 (diamond-like) carbon to sp2 (graphite-like) carbon.The methods also provide for lower processing pressures, lowerprocessing temperatures, and higher processing powers, each of which,alone or in combination, may further increase the relative fraction ofsp3 carbon in the deposited amorphous carbon layer. As a result of thehigher sp3 carbon fraction, the methods described herein provideamorphous carbon layers having improved density, rigidity, etchselectivity, and film stress as compared to amorphous carbon layersdeposited by conventional methods.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

The invention claimed is:
 1. A method of processing a substrate,comprising: positioning a substrate on a substrate support disposed in aprocess volume of a process chamber; flowing a process gas comprising ahydrocarbon gas and a diluent gas into the process volume, a flowrateratio of the hydrocarbon gas to the diluent gas being between about 1:10and about 10:1; maintaining the process volume at a pressure less thanabout 50 mTorr; forming a plasma of the process gas by applying a firstpower to a first electrode of the process chamber and applying a secondpower to a second electrode of the process chamber, wherein the secondpower is a first pulsed DC power; maintaining the substrate support at atemperature less than about 350° C.; exposing a surface of the substrateto the plasma; and depositing an amorphous carbon layer on the surfaceof the substrate.
 2. The method of claim 1, wherein the amorphous carbonlayer has a density of more than about 1.8 g/cm³ and has a Young'smodulus of more than about 150 GPa.
 3. The method of claim 1, whereinthe amorphous carbon layer has a film stress of less than about 500 MPa.4. The method of claim 1, wherein the hydrocarbon gas comprises one ofCH₄, C₂H₂, C₃H₈, C₄H₁₀, C₂H₄, C₃H₆, C₄H₈, C₅H₁₀, or a combinationthereof.
 5. The method of claim 4, wherein the temperature is less thanabout 100° C. and the pressure is less than about 20 mTorr.
 6. Themethod of claim 5, wherein the diluent gas comprises H₂, and wherein aflowrate ratio of H₂ to the hydrocarbon gas is between about 0.5:1 andabout 1:10.
 7. The method of claim 1, wherein the first power is an RFAC power between about 500 W and 5 kW, with a frequency between about350 kHz and about 100 MHz, and wherein the second power is between about200 W and about 15 kW and is pulsed at a frequency of about 1 kHz. 8.The method of claim 1, wherein the first electrode is disposed in thesubstrate support and the second electrode is disposed opposite thesubstrate support and wherein the second electrode is a showerhead. 9.The method of claim 1, wherein the second electrode is disposed in thesubstrate support and the first electrode is disposed opposite thesubstrate support.
 10. The method of claim 9, wherein: a lid assembly ofthe process chamber includes a third electrode; and the method furthercomprises: applying a third power to the third electrode, the thirdpower being a second pulsed DC power.
 11. A method of processing asubstrate, comprising: positioning a substrate on a substrate support,the substrate support disposed in a process volume of a process chamber;flowing a process gas comprising a hydrocarbon gas and a diluent gasinto the process volume; maintaining the process volume at a pressureless than about 20 mTorr; forming a plasma of the process gas byapplying an RF AC power to a first electrode of the process chamber,wherein the RF AC power is between about 500 W and 5 kW with a frequencybetween about 350 kHz and about 100 MHz and applying a first pulsed DCpower to a second electrode of the process chamber, the second electrodedisposed in the substrate support, wherein the first pulsed DC power isbetween about 200 W and about 15 kW; maintaining the substrate supportat a temperature less than about 100° C.; exposing a surface of thesubstrate to the plasma; and depositing an amorphous carbon layer on thesurface of the substrate by plasma enhanced chemical vapor deposition.12. The method of claim 11, wherein the hydrocarbon gas comprises one ofCH₄, C₂H₂, C₃H₈, C₄H₁₀, C₂H₄, C₃H₆, C₄H₈, C₅H₁₀, or a combinationthereof.
 13. The method of claim 12, wherein the diluent gas comprisesH₂, and wherein a flowrate ratio of H₂ to the hydrocarbon gas is betweenabout 0.5:1 and about 1:10.
 14. The method of claim 11, wherein thefirst electrode is disposed opposite the substrate support.
 15. Themethod of claim 14, wherein: a lid assembly of the process chamberincludes a third electrode; and the method further comprises: applying athird power to the third electrode, the third power being a secondpulsed DC power.